This invention relates generally to heat exchangers and, more particularly, to multiple tube bank heat exchanger for use in an air-cooled chiller.
In a conventional air conditioning system, the condenser of the refrigeration circuit is located exterior to a building. Typically, the condenser includes a condensing heat exchanger and a fan for circulating a cooling medium (e.g., air) over the condensing heat exchanger. The air conditioning system further includes an indoor unit having an evaporator for transferring heat energy from the indoor air to be conditioned to the refrigerant flowing through the evaporator and a fan for circulating the indoor air in a heat exchange relationship with the evaporator.
Air-cooled condensers, including air-cooled chillers and rooftops, are often used for applications requiring large capacity cooling and heating. Because larger condenser heat exchanger surfaces are needed for the functionality of the system, the condenser generally includes a plurality of condensers units. Multiple fans are located on top of the condenser housing for each unit.
Historically, these heat exchangers in condensers have been round tube and plate fin (RTPF) heat exchangers. However, all aluminum flattened tube serpentine fin heat exchangers are finding increasingly wider use in industry, including the heating, ventilation, air condition and refrigeration (HVACR) industry, due to their compactness, thermal-hydraulic performance, structural rigidity, lower weight and reduced refrigerant charge, in comparison to conventional RTPF heat exchangers. Flattened tubes commonly used in HVACR applications typically have an interior subdivided into a plurality of parallel flow channels. Such flattened tubes are commonly referred to in the art as multi-channel tubes, mini-channel tubes or micro-channel tubes.
A typical flattened tube serpentine fin heat exchanger includes a first manifold, a second manifold, and a single tube bank formed of a plurality of longitudinally extending flattened heat exchange tubes disposed in spaced parallel relationship and extending between the first manifold and the second manifold. The first manifold, second manifold and tube bank assembly is commonly referred to in the heat exchanger art as a slab. Additionally, a plurality of fins are disposed between the neighboring pairs of heat exchange tubes for increasing heat transfer between a fluid, commonly air in HVACR applications, flowing over the outside surfaces of the flattened tubes and along the fin surfaces and a fluid, commonly refrigerant in HVACR applications, flowing inside the flattened tubes. Such single tube bank heat exchangers, also known as single slab heat exchangers, have a pure cross-flow configuration.
Double bank flattened tube and serpentine fin heat exchangers are also known in the art. Conventional double bank flattened tube and serpentine fin heat exchangers are typically formed of two conventional fin and tube slabs, one positioned behind the other, with fluid communication between the manifolds accomplished through external piping. However, to connect the two slabs in fluid flow communication in other than a parallel cross-flow arrangement requires complex external piping and precise heat exchanger slab alignment. For example, U.S. Pat. No. 6,964,296 B2 and U.S. Patent Application Publication 2009/0025914 A1 disclose embodiments of double bank, multichannel flattened tube heat exchanger.